In the treatment of some diseases or defects associated with a patient, it has been found necessary to access specific targets within the patient. For example, in neurosurgery, it has been found necessary to access specific targets within the patient's brain. In neurosurgery, the specific targets are typically located and identified by one of a number of techniques. Sometimes the target can be visualized using magnetic resonance imaging (MRI). MRI has been developed as an imaging technique adapted to obtain both images of anatomical features of patients as well as some aspects of the functional activities of biological tissue.
Once a target has been identified, neurosurgery involves making a drill hole in the relatively thick bony structure surrounding the brain (i.e., the skull). The drill hole is made by a surgeon at a desired entry point using a surgical drill. The surgeon then typically guides (e.g., using trajectory guide tubes) one or more surgical instruments or observation tools (e.g., electrodes—recording or stimulating, cannulas, needles, biopsy instruments, catheters or other types of probes or devices) through the entry hole to the specific targets within the brain. At least two challenges involved in neurosurgery include staying oriented within the brain, and directing instruments to a desired depth therein. To satisfy the former of these two challenges, according to one technique, both the aiming of the instrument guide and the subsequent introduction of the instrument are conducted while a patient's skull is positioned within an enclosure (i.e., a bore) of an MRI scanner. Through the use of the MRI scanner, the surgeon is able to verify the orientation of each instrument introduced. Unfortunately, however, using such technique the surgeon is currently unable to also remotely determine the position (e.g., depth) of the instrument introduced. Instead, to determine the depth of the instrument, the surgeon must leave his/her position near an imaging display and enter the MRI-generated magnetic field and manually read the instrument depth.
Some drawbacks of the MRI technique are rooted in the fact that the corresponding magnetic field often presents problems with electrical components, such as the electrical components of conventional electronic measuring apparatus. The use of electrical components may not work in the strong magnetic field surrounding an MRI scanner for at least three reasons. First, their components (e.g., metal wires, electrical components, etc.) may experience a force in the magnetic field, creating a safety hazard for the patient. Second, the accuracy with which such components operate may be affected by the magnetic field. Third, it puts patients at risk for burns due to eddy currents generated within conductive components.
It is with this recognition of the foregoing state of the technology that the present assemblies and methods providing remote position detection in an electromagnetic field have been conceived and are now set forth in text and drawings associated with this patent document.